Pulsed Laser Deposition (PLD) is a method for growth of chemically complex materials, oftentimes allowing for stoichiometric transfer of the target material to the substrate that supports the deposited film. In some cases, though, target stoichiometry is preserved only under very specific deposition conditions that vary depending on the target material and the substrate temperature. Such conditions are often difficult and time-consuming to determine.
Prior methods used to address this problem include: (1) use of multiple ablation targets (on a trial-and-error basis) to determine the exact target composition needed to produce the desired film composition, (2) use of a split target (or two separate single-composition targets), with different laser dwell times on each target half (by alternatively ablating each target half, spending a different amount of time on each half), but without target rotation combined with laser beam rastering (continuous back and forth motion), and (3) use of a split or sectioned target that is rotated around a point not coincident with the target center (varying the distance between the rotation point and the target center to achieve various film compositions), but with no laser beam rastering.
Prior method 1 is time consuming and expensive, requiring the manufacture or purchase of numerous targets of various compositions. Prior method 2 can result in alternating layers of the target material halves, requiring post-deposition annealing to achieve a homogeneous film, and non-uniform target surface usage. Prior method 3 requires a special mechanism for the off-target-center rotation (or a smaller target than would be used for on-target-center rotation) and does not incorporate laser beam rastering to maximize target surface usage and ablation uniformity.
The method disclosed herein uses PLD with a single two-part (split) ablation target to grow thin layers of multi-component films with control over the resultant film elemental composition, while still rotating the target about its center to maximize target usage (or coverage) and to more uniformly ablate the target surface.